Control circuit



W. L. MORRIS CONTROL CIRCUIT Feb. 3, 1953 Filed Oct. 1, 1951 DRILL MOTOR THERMOELECTRIC SWITCH FIG. .2

INVENTOR.

W.L.MORRIS A ORNEVS Patented Feb. 3, 1953 CONTROL CIRCUIT William L. Morris, Bartlesville, kla., assignor to Phillips Petroleum Company, a corporation of Delaware Application October 1, 1951, Serial No. 249,047

13 Claims.

This invention relates to a control circuit. In a more specific aspect, it relates to a protective system for an electric drilling device.

Various systems have been proposed for earth drilling in which an electric motor and drill bit assembly is lowered into the hole by a cable so that the cable need only support the drilling assembly and need not transmit the drilling torque from the surface to the drill bit. Such drills ordinarily incorporate a device for preventing rotation of the drilling assembly in response to rotation of the motor contained therein, this device usually consisting of friction dogs which bite into the sides of the drill hole and thereby.

prevent rotation of the drilling assembly in the direction in which it tends to turn under the influence of motor and bit rotation, the friction dogs disengaging upon rotation of the assembly in the opposite direction to permit raising and lowering of the assembly in the drill hole.

A problem which has been quite troublesome in the operation of such drilling assemblies is the overheating of the drill bit. Insofar, as I am aware, no one has previously proposed a system for sensing such overheating of the drill bit and providing means to prevent further rotation of the assembly when such overheating occurs.

The circuits which I have devised to solve this problem are useful not only in rotary drilling assemblies, but also in many other applications where a controlled device is located remotely from its power source, and in which the controlled device is relatively inaccessible.

It is an object of the invention to provide an improved control circuit for a controlled device.

It is a further object to provide a device for sensing overheating of the drill bit in a rotary drilling assembly.

It is a still further object to provide a system for stopping rotation of the motor when overheating of the drill bit occurs.

It is a still further object to provide a structure and circuit which is reliable in operation, of simple construction, and which can be manufactured and installed at a low cost.

Various other objects, advantages and features of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

Figure 1 is a front elevational view, partially in section, of electric drilling apparatus embodying the principles of this invention; and

Figure 2 is a schematic circuit diagram of the control circuit of this invention.

Referring now to the drawings in detail and particularly to Figure 1, I have shown the invention as applied to a drilling assembly comprising a cable ill by which the assembly is lowered into or raised from a bore hole, this cable being connected by a swivel II to the main body of the drilling assembly. The swivel prevents twisting of the cable in the event that the anti-rotation device hereinafter described fails to operate.

The drilling assembly further includes :an antirotation device [2 incorporating a plurality of friction dogs l3. The initial rotation of the drill ing assembly causes these friction dogs to bite into the sides of the bore hole, thereby preventing further rotation of the assembly itself and permitting the drill bit to function in the usual manner. These friction dogs are disengaged from the sides of the bore hole upon rotation of the assembly in the opposite direction thereby permitting it to be raised from or lowered into the bore hole.

Mounted below the anti-rotation device I2 is a casing 14 having an electric motor l5 mounted therein. This motor can be of the squirrel-cage induction-type and is considerably elongated so that the requisite power can be obtained for driving the drill bit. Interposed between the motor and anti-rotation device is a bailer [B in which cuttings are deposited through operation of a fluid circulating system in the operation of the drilling assembly. This liquid circulation is effected by a pump ll carried within the casing l4 and operated to circulate cooling fluid through. suitable orifices, not shown, in the drill bit after which the fluid passes upwardly between the casing and the walls of the bore hole to the top of the bailer wherein it is admitted through suitable openings, not shown, and returns to the pump to complete the circulatory system.

The motor I5 is connected through reduction gearing I8 with a metal drill bit I?) having a metal body portion Zil carrying the usual cutters 2!. It will be noted that the drill bit is connected to reduction gearing It by a shaft 22 and the reduction gearing, in turn, is connected by a shaft with the motor l5.

In accordance with the invention, a sensing or condition responsive device, such as a thermoelectric switch 24, is embedded within the metal body 26 of the drill bit so that the switch is in thermal contact with the metal of the: drill bit.

This switch, which may be any of the usual thermoelectric switches, is preferably of the snap. action type so that a rapid actuation of the switch occurs when the temperature of the drill bit rises above a predetermined value. Preferably and advantageously, the switch contacts are normally open, and they are closed by snap action when the switch is operated.

The switch 24 is connected by leads 25, 23 which extend through the shaft 22 to a pair of slip rings 21, 28. Cooperating with the slip rings 2?, 28 are a pair of brushes 29,353 from which leads 3!, 32 extend to a housing 33 containing the control elements of this invention. It will be noted that, by the slip rings and brushes, the switch 23 on the rotating drill bit is connected to the control housing 33 which is stationary with respect to the casing l4.

Also connected to the housing 33 are leads 33, 35 and 35. Lead 34 extends to the motor 65, lead 35 is a ground connection, and lead 33 is connected to a conductor forming a part of cable H3 and extending to the surface apparatus hereinafter described.

Referring now to Figure 2, in which parts similar to those described in connection with Figure l are indicated by like reference characters, the apparatus within housing 33 includes a battery 38 or other source of direct current, a first relay 39 having a normally closed set of contacts 43 and a normally open set of contacts ii, together with a second relay 42 having a normally closed set of contacts 43. Finally, this apparatus includes a filter 44 which permits the passage of direct current but blocks the passage of alternating current.

It will be noted that the operating winding of relay 39 is connected in circuit with battery 38, the slip rings 21, 28 and the thermoelectric switch 24. Relay 33 also has a holding circuit which includes the battery 38, a lead 43, the normally closed contacts 43, and the normally open contacts 4|. Relay 42, which opens the holding circuit when actuated, has an operating circuit extending through filter 44 to ground and the conductor 36.

At the surface, conductor 36 is connected in circuit with a switch 53 and a source of alternating current which may be a motor generator or a utility line. Also connected in circuit with the source 5! and switch 53 is an ammeter 52. Conductor 36 can also have a direct voltage applied thereto through a circuit which includes a direct current source 53 and a switch 54.

The operation of the system will now be apparent to those skilled in the art. In normal operation of the drilling unit, upon closure of switch 50, drilling motor i5 is supplied with alternating current through conductor 35 from source 5|. Thermoelectric switch 23 is open so that no energizing current is supplied to the operating winding of relay 39, and the alternating current present at conductor 36 cannot energize the operating winding of relay 32 since passage thereof is blocked by the filter 44.

Should overheating of the drill bit occur, switch 24 is closed when the drill bit temperature rises above a predetermined value. This closes the operating circuit of relay 3.), thereby opening contacts 43 and interrupting the operation of the motor. This, in turn, causes the reading at meter 52 to drop to zero, thereby apprising the surface operator that operation of the drill motor has been interrupted by the control device.

It will be'noted that the described operation of relay 39 closes contacts ii and completes the holding circuit of relay 39 through contacts 13 and battery 38. Accordingly, the drill motor I5 remains de-energized even after the drill bit temperature falls sufficiently as to open thermoelectric switch 24.

In some cases, the overheating may be caused by a temporary blockage in the cooling fiuid circulation system. In such case, operation can be resumed without removing the drilling assembly from the bore hole. To accomplish this purpose, the operator at the surface closes switch 54, thereby impressing direct current upon the operating winding of relay 52 through filter 34. Operation of relay 32 opens contacts 43 and thereby the holding circuit of relay 33. If the drill bit is sufficiently cool to permit safe operation, switch 23 is also open so that relay 39 is tie-energized with resultant closure of contacts 33 and the motor operating circuit.

Should overheating of the drill hit again develop, it is probably advisable to remove the drilling assembly from the hole to determine the cause of overheating.

It will be apparent that I have achieved the object of my invention in that operation of the drill motor i5 is automatically stopped when the drill bit temperature becomes excessive. Knowledge of this condition is transmittedto the operator at the surface, by the indication of meter 52, who must manually close switch 53 before operation of the system can be resumed. Where desirable, the operation can be resumed without removing the drilling assembly from the bore hole.

It will be further evident that the control circuit of my invention has many applications in other fields where a controlled device is subjected to a dangerous condition, and the controlled device is remote from its source of power and controlling means. Finally, it will be evident that the principles of my invention can be applied to other types of drilling systems wherein the power for rotating the drilling bit can be furnished by a prime mover located at the surface of the bore hole.

While the invention has been described in connection with a present, preferred embodiment thereof, it is to be understood that this description is illustrative only and is not intended to limit the invention.

I claim:

1. The combination, with an electric drilling assembly, and a cable for lowering said assembly into a bore hole, said assembly comprising a casing, an electric motor mounted in said casing, friction dogs mounted on said casing to prevent rotation of the casing in said bore hole, a shaft driven by said motor, and a metal drill bit driven by said shaft, of a source of alternating current, a switch and a meter connected in circuit therewith, a source of direct current, and a switch connected in circuit therewith, all mounted at the top or said drill hole, a conductor carried by said cable, means for selectively connecting said sources to said conductor, a first relay mounted in said casing having a normally open and a normally closed set of contacts, a second relay mounted in said casing having a normally closed set or" contacts, a battery and filter for blocking alternating current mounted in said casing, a thermoelectric switch in thermal contact with said drill bit, said switch closing when the drill bit temperature rises above a predetermined value, a pair of slip rings carried by said shaft, leads connecting said switch in circuit with said battery, said slip rings, and the operating winding of said first relay, leads connecting said conductor through the normally closed contact set of said first relay to said electric motor, and through said filter to the operating winding of said second relay, a ground return for said electric motor and said filter, and a holding circuit including said battery, the operating winding and normally open contact set of said first relay, and the normally closed contact set of said second relay.

2. The combination, with an electric drilling assembly, and a cable for lowering said assembly into a bore hole, said assembly comprising a casing, an electric motor mounted in said casing, an anti-rotation device mounted on said casing, and a metal drill bit driven by said motor, of a source of alternating current, a meter connected in circuit therewith, and a source of direct current all mounted at the top of said drill hole, a conductor carried by said cable, means for selectively connecting said sources to said conductor, a first relay mounted in said casing having a normally open and a normally closed set of contacts, a second relay mounted'in said casing having a normally closed set of contacts, a battery and a filter for blocking alternating current mounted in said casing, a thermoelectric switch in thermal contact with said drill bit, said switch closing when the drill bit temperature rises above a predetermined value, means for connecting said switch in circuit with said battery and the operating winding of said first relay, a lead connecting said conductor through the normally closed contact set of said first relay to said electric motor, and through said filter to the operating winding of said second relay, a ground return for said electric motor and said filter, and a holding circuit including said battery, the operating winding and normally open contact set of said first relay, and the normally closed contact set of second relay.

3. The combination, with an electric drill, and a cable for lowering said drill into a bore hole, said drill comprising a casing, an electric motor mounted in said casing, anti-rotation means mounted on said casing, and a metal drill bit driven by said motor, of a source of motor operating current at the top of said drill hole, a conductor carried by said cable, means for connecting said source to said conductor, a relay mounted in said casing, said relay having a normally closed set of contacts, current supplying means mounted in said casing, a thermoelectric switch in thermal contact with said drill bit, said switch closing when the drill bit temperature rises above a predetermined value, means connecting said switch in circuit with said battery and the operating winding of said relay, a, lead connecting said conductor through said normally closed contact set to said electric motor, a holding circuit for said relay, and means for breaking said holding circuit.

4; The combination, with an electric drill, and a cable for lowering said drill into a bore hole, said drill comprising a casing, an electric motor mounted in said casing, friction dogs mounted on said casing to prevent rotation of the casing in said bore hole, and a metal drill bit driven by said motor, of a source of motor-operating current at the top of said drill hole, a conductor carried by said cable, means for connecting said source to said conductor, a relay mounted in said casing, said relay having a normally closed set of contacts, current supplying means mounted in said casing, a thermoelectric switch in thermal contact with said drill bit, said switch closing when the drill bit temperature rises above a preselected value, means connecting said switch in circuit with said current supplying means and the operating winding of said relay, and a lead connecting said conductor through said normally closed contact set to said electric motor.

5. The combination, with an electric drill an a cable for lowering said drill into a bore hole, said drill comprising a casing, an electric motor mounted in said casing, friction dogs mounted on said casing to prevent rotation of the casing in said bore hole, a shaft driven by said motor, and a metal drill bit driven by said shaft, of a current source for operating said motor, and operating circuit having a conductor associated with said cable to connect said current source to said motor, a thermoelectric switch in thermal contact with said drill bit, said switch operating when the drill bit temperature rises above a predetermined value, and means responsive to the operation of said switch to break said operating circuit.

6. The combination, with a metal drill, and a motor for rotating said drill, of a thermo-responsive electric switch in contact with said metal drill, said switch being actuated when the drill temperature rises above a selected value, and control means responsive to the actuation of said switch to stop said motor.

'7. The combination, with a metal drill, and a motor for rotating said drill, of a thermo-responsive electric switch in contact with said metal drill, said switch being closed when the drill temperature rises above a selected value, and control means responsive to the closure of said switch to stop said motor, said control means including a current source, a relay having a set of normally closed contacts connected in circuit with said motor, and means connecting said switch in circuit with said current source and the operating winding of said relay.

8. The combination, with a metal drill, and a motor for rotating said drill, of a thermo-responsive electric switch in contact with said metal drill, said switch being closed when the drill temperature rises above a selected value, and control means responsive to the closure of said switch to stop said motor, said control means including a current source, a relay having a set of normally closed contacts connected in circuit with said motor, means connecting said switch in circuit with said current source and the operating winding of said relay, a holding circuit for said relay, and means for breaking said holding circuit.

9. A control circuit including an electrical device to be controlled, a relay having a set of normally closed contacts, a source of direct current and a source of alternating current remote from said controlled device, an operating circuit for said device including said normally closed set of relay contacts, and said source of alternating current, a sensing element, means controlled by said sensing element to energize the operating winding of said relay, a holding circuit for said relay, and a device connected in circuit with said direct current source for breaking said holding circuit.

10. A control circuit including an electrical device to be controlled, at first relay having a set of normally open contacts and a set of normally closed contacts, a second relay having a set of normally closed contacts, a filter for blockin alternating current, a source of alternating current remote form said controlled device, a switch and an ammeter connected in circuit with said current source, a source of direct current remote from said controlled device, a switch connected in circuit therewith, an operating circuit for said controlled device including said alternating current source, the switch associated therewith, said meter, and the normally closed contacts of said first relay, a condition-responsive device for energizing the operating winding of said first relay, a holding circuit for said first relay including a current source, the normally open contacts of said first relay and the normally closed contacts of said second relay, and means connecting the operating winding of said second relay in circuit with said filter, said source of direct current, and the switch associated therewith.

11. In combination, a metal drill bit, and a thermo -responsive electric switch in thermal contact with .said metal drill bit, said switch being actuated when the drill bit temperature rises above a selected value.

12. In combination, a metal drill bit having a body and a .plurality of cutting surfaces, and a theme-responsive electric switch embedded in the metal body of said drill bit and in thermal contact therewith, said switch being closed when the drill bit temperature rises above a selected value.

13. The combination, with a metal drill, and a prime mover for rotating said drill, of temperature sensing means in thermal contact with the metal of said drill, said sensing means being actuated when the temperature of said metal rises above a selected value, and control means responsive to the actuation of said sensing means to interrupt the operation of said prime mover.

WILLIAM L. MORRIS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

